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This paper presents the development of broadband antireflection coating for a high-index substrate such as Si using SiN x /SiO2 by inductively coupled plasma chemical vapour deposition (ICP-CVD). The thin-film design employs a simulated annealing method for a minimal average reflectance over the wavelength range and incidence angles involved, which gives the optimized refractive index and thickness of each layer of the thin-film stack under different layer numbers. Using ICP-CVD, the SiN x material system is optimized by tuning the SiH4/N2 gas ratio. The corresponding thin-film characterization shows the precise refractive index/film thickness control in deposition, and the deposited film also has a low absorption coefficient and smooth surface. The double-layer SiN x /SiO2 coating with the optimized refractive index and thickness for broadband antireflection is demonstrated experimentally. The average reflectance of the Si surface is reduced from ~32% to ~3.17% at normal incidence for a wavelength range from 400 to 1100 nm.

We demonstrated low-temperature bonding of III–V InP-based compound semiconductor on silicon via nano-thin SiO2 interlayer down to thickness of 20 nm, with ultra-smooth surface for heterogeneous photonic integration. The bonding is achieved with chemical cleaning of the sample surface, followed by oxygen plasma surface activation, which gives high quality bonding between the two different materials. Detail analyses on the bonded samples are carried out. From the photoluminescence and the x-ray diffraction measurements, in which no significant peak shift and peak broadening are observed, we conclude that the crystalline quality of the bonded thin film is preserved. The cross-sectional high resolution transmission electron microscopy shows that bonded III–V-SiO2–Si interface has no observable defect. These results reinforce that the proposed bonding offers a promising technology for realizing versatile heterogeneous photonics integration.

Patterned gallium nitride nanowires have been grown on n-Si(100) substrates by pulsed laser ablation. The nanowires are patterned using a physical mask, resulting in regions of nanowire growth of different density. These gallium nitride nanowires are single-crystalline with hexagonal wurzite structures. The electrical transport measurements of individual GaN nanowires show near-linear current–voltage characteristics. The estimated electron densities of these individual GaN nanowires range from 1.8–6.8 × 1018 cm−3. The field emission characteristics of these patterned gallium nitride nanowires show a turn-on field of 8.4 V µm−1 to achieve a current density of 0.01 mA cm−2 and an enhanced field emission current density as high as 0.96 mA cm−2 at an applied field of 10.8 V µm−1. The field emission results indicate that, besides crystalline quality as well as the low electron affinity of gallium nitride, density difference in the nanowires growth greatly enhances their field emission properties by reducing the screening between nanowires.